Composting in the Subarctic – Operations

Unloading Actium Batch Rotary Composter

The Actium compost drums are used in a variety of climates. In the tropical and subtropical climates, the composter is used year-round. In temperate climates, the Actium Batch Compost Drum can be used year-round because the drum is insulated. However, the decaying process can be slowed where winter temperatures are below freezing for a prolonged period. There are two approaches to maintain hot composting temperatures when ambient temperatures are below freezing. One approach is to use an Actium Batch Compost Drum that includes a heating coil. The other approach is to place the composter in a sheltered area.

In subarctic or arctic climates, maintaining composting temperatures during the winter season can be challenging when outside temperatures are regularly below -15°C ( 5°F) – leaving limited options for (sub)arctic composting. One option is to have the Actium Batch Compost Drum in an insulated building to allow for year-round composting. The other option is not to compost during the winter season. In the subarctic community of Fort Albany First Nation (FAFN), Ontario, Canada, they chose only to compost from late May to early October. This article provides an overview of the composting operations applied in FAFN, and I discuss some alternative approaches. Many details in this article can be used to operate an Actium Batch Compost Drum in other climates

Spring (Late May)

By late-May, the Albany river is no longer covered in ice, and most of the snow has melted. At this time, the composter manager prepares the Actium Batch Compost Drum for another season of composting. In the upcoming 2021 season, we plan to start the compost earlier – in April – to increase the number of compost batches per growing season.

Checking if the composter is level

The first task is to ensure the Actium Batch Compost Drum is level. It is ideal to have the composter on a cement pad, though that was not an option in FAFN. Instead, the composter is located on a flat gravel area that can subside after freezing and thawing due to the region’s geomorphology. Filling an unlevel composter with organics can cause strain on the crank, chain, and supports. When the composter is not level, we lift the empty composter using a log as leverage (as a substitute, a forklift or tractor can be used) and repair the uneven side. The ideal placement of the Actium Batch Compost Drum would be on a level concrete pad.

Chain inspection

Next, we check that the chain is fitted snug to the crank, and we turn the crank both clockwise and counter-clockwise to make sure it is in working condition.

Adding Organics

Once the composter meets our spring inspection, we start to add organics. We add both green and brown materials in equal volume. This upcoming 2021 season, we plan to fill the compost drum 1/4 full of brown materials (i.e. sawdust, shredded paper and cardboard). Starting the composter with extra brown materials will help regulate moisture when wet green materials begin to decompose. As well, we plan to add a garden shovel full of soil to help accelerate the compost.

Summer – Early Fall (July – September)

Twice a week throughout the summer, the compost manager adds green and brown types of organic waste. When organics are added to the composter, the drum is fully rotated at least three times in a clockwise direction – to mix newly added organics with existing decomposing materials. The Actium Compost Drum can handle up to 50 lb (23 kg) of organic waste per day – giving a total allowance of 350 lb (159 kg) per week. We add approximately 60 to 200 lb (27 – 91 kg) per week depending on the organic amount supplied to us by the FAFN organizations participating in the compost program.

Monitoring temperature, moisture, and odours

Throughout the summer, we monitor temperature, moisture and odours. When one (or all) of these issues occur, we take measures to improve decomposition activity. Troubleshooting for these issues are discussed in previous posts: Regulating Compost Moisture during Hot Composting (January 17, 2020), Compost Temperatures (December 18, 2019), and Greens and Browns: Compost Input Management (March 3, 2020). We are happy with the compost produced in FAFN. However, closer monitoring of compost moisture and temperate would improve the decomposition rates and allow for an additional compost batch.

The drum approaching full

The Actium Compost Drum can hold a volume of 1.56 m3 ( 55 ft3 or 411 gal) and a mass up to 2000 lb (907 kg). When the composter is near full, we add organics less frequently. Organics will continue to decompose, and this will permit more space for new organic additions. In FAFN the composter usually approaches near full by the end of-August. Currently, we only do one compost batch per year, so we allow the organics to continue to decompose in the Actium Batch Drum into the late summer /early fall. In the late summer, we add more browns to control compost moisture and supply additional carbon to decomposer microbes. Additionally, we ensure that we turn the Actium Batch Compost Drum weekly – even when no new organics are added to the composter.

Alternative approaches

In a scenario where the compost was near full by July, we would have the ability to create two batches of compost within a growing season. In that case, we would empty the Actium Batch Compost Drum. This first compost batch would be placed in a resting area, and we would start a new batch in the composter. 

Fall (October)

In October, we dedicate approximately an hour to empty and winterize the Actium Batch Compost Drum. Emptying the Actium Batch Compost Drum in the fall allows for a quick start-up when the warm weather arrives in the following spring. 

Emptying the composter

Emptying the composter is easy. First, we turn the drum counter-clockwise a few times to loosen the compost. Secondly, the lid is removed. The drum is then rotated counter-clockwise until the drum opening is in the desired position to empty the composter. In previous years we allowed the compost to fall onto a tarp placed directly under the drum. More recently, we created a tarped ramp (shown in the picture) for the compost to be moved and piled beside the composter. Then we shovel the compost to a secondary resting location. 

Secondary resting location

In our first year with the Actium Batch Compost Drum, we covered the compost with a tarp. In recent years we opted to modify an intermediate bulk contain (IBC) to store the compost over winter (shown in picture). We cut off the top of the IBC to add compost with ease. When the IBC is filled with compost, we tightly cover the IBC with a tarp to prevent snow and rain from accumulating into the container.

Compost removed from the Actium Batch compost needs to rest before it is used to nourish plants. Decomposer microbes active in fresh compost can be harmful to growing plants. It is suggested that fresh compost rest for 2-3 weeks before being used on plants. In FAFN this resting period occurs when the compost is in the IBC during the winter season.

Winterizing the Actium Batch Compost Drum

Winterizing the Actium Batch Compost Drum is simple. We clean around the drum opening and reattach the drum lid.  We add grease to the crank chain to prevent rust – considering the composter will be in a stationary position from October to April.

Following Spring (April/ May)

When warmer weather arrives, the compost in the IBC is ready to distribute throughout the FAFN community – to the community garden, the school greenhouse, and those with gardens at their homes.

Composting in the Subarctic – Materials

Sourcing Organic Materials in Fort Albany

Determining and sourcing organic materials for Composting

Along with having the right composter for the task,  the Fort Albany First Nation (FAFN) community needed to determine what organic materials would be added to the Actium Batch Compost Drum and where we could obtain these materials. There are two types of organic materials we wanted to hot compost – “greens” (C:N <30) and “browns” (C:N>30). This article shares what green and brown organic materials we add to the FAFN compost. For more information on why mixing green and brown organic materials is important for hot composting,  please scroll down to our March 3, 2020 post.

Fort Albany First Nation is a relatively small isolated community; it has a residing population of 900. The community is located in the far north of Ontario, along the Albany River and is within the Boreal forest. When community members of FAFN want local foods, they harvest from the land (i.e. hunting geese or moose, fishing, or picking berries). However, the diet of the majority of families in the community comprises mostly of imported foods. Other non-food types of organic materials are also imported to the community as well – such as paper products. Both local and imported materials were used to create compost in FAFN.

Sourcing green materials

The main green organic materials used in the FAFN compost are from locally hunted non-edible portions of Canadian geese, and imported fruit and vegetable wastes. Canadian geese are hunted in April and in late June. The geese are then prepped to be smoked for preservation or baked in an oven. Those who prep the geese put aside the head, wings, feet, innards and feathers to be picked up for hot composting. The Actium Batch Compost Drum was ideal for composting geese remnants as it is designed to decompose poultry deadstock safely. 

The imported vegetable and fruit wastes added to the composter were collected within the community from the grocery store, a convenience store, the school breakfast program, and the monthly occurring Farmer’s Market. We arranged an organic waste collection process with store and program managers.  This process entails providing each establishment with a large tote to fill with spoiled produce. Our compost program manager goes to each establishment regularly to pick up the totes. Before our compost program manager adds produce waste to the composter, they chop up large or whole items (such as melons, corn, carrots, or celery) to allow for faster decomposition. They also remove any foreign materials (i.e. plastic wrappings or rubber bands) to maintain compost quality.  The green materials are then added to the Actium Batch Compost Drum, along with brown materials. The drum door is then closed, and we rotate the drum two to three times to mix the newly added organic materials with the other decomposing materials. Afterwards, the empty totes are rinsed and returned to each establishment.

Sourcing brown materials

Brown materials used to create FAFN compost includes wood shavings, shredded paper and dried grass and leaves. We situated our Actium Batch Compost Drum in the local sawmill yard to make it convenient to add wood shavings while adding green organic wastes. The shredded paper is donated from the school, hospital, and Farmer’s Market.  The paper sourced from the Farmer’s Market is ideal as it is blank newsprint used to protect fruit and vegetables during transport to FAFN.  Similarly, to picking up green organic waste, the compost program manager goes to these establishments to pick up the paper waste. We collect dried grasses and leaves from the FAFN’s agroforestry community garden during our spring clean-up. 

Diversifying both green and brown materials is ideal as it combines materials with differing C:N ratios and various decomposition rates. We are interested in expanding our list of organic materials added to the compost, such as decomposing the non-edible portions of fish and food-grade cardboard. Before the FAFN compost program was in place, these organic materials – both local and imported – were destined for the landfill or were underutilized as a nutrient resource.  With the compost program in place, these organic materials are now utilized to make a local low-cost soil amendment to nourish gardens in FAFN. 

Composting in the Subarctic – Design

Batch Composter with No Steps

Our Ideal Design

The Actium Batch Compost Drum has become an essential tool for Fort Albany First Nation’s community garden. This article details why Fort Albany First Nation needed a composter and why the design of the Actium Batch Compost Drum suited our needs.

Why was a composter needed in a remote subarctic community?

Fort Albany First Nation (also known as Peetabeck) is a remote and subarctic fly-in community of 900 people.  The community situates at 5220’N and 8146’W in the Muskegowuk Cree territory, on the west coast of James Bay, Ontario.  Those who live in Fort Albany First Nation are concerned about food insecurities, which is a similar concern to others who reside in far-north communities. Many living in remote northern communities rely on non-local food that is expensive due to the long-distance transport costs.  As well, harvesting local traditional foods is becoming a challenging activity due to climate and migration shifts, and the increased risks associated with travelling further distances to hunt, fish and forage.

Though food security challenges emerged with the rising global temperatures, there are also opportunities to adapt to changes occurring in the northern environment.  One adaptation strategy Fort Albany First Nation has welcomed is the creation of gardens (funded by that Canadian Institute of Health Research and Climate Change Health and Adaptation Program).  As of 2019, over 28 different crop species grew in the Fort Albany First Nation community garden. During crop harvest nutrients are removed from the soil; nutrients need to be added back to the soil to maintain fertility.  The Actium Batch Compost Drum was our solution for creating local fertilizer in this remote community.  We need to have locally made fertilized because importing fertilizers into the community would be a costly, impractical, and unsustainable option.

An ideal design for a community composter

The design of the Actium Batch Compost Drum met the criteria for a compost system in Fort Albany First Nation.  Our desired design features included being lifted off the ground, closed and contained, an insulted drum, and mechanically operated. 

Lifted off the ground

We preferred a composter that was lifted off the ground to prevent nutrient loss through run-off and leaching, and to protect the compost from flood events. The land where Fort Albany First Nation sits is characterized as flat and near sea-level. During the spring thaw, the land can be excessively wet and is susceptible to floods. 

Closed and contained

Closed and contained was a central feature we wanted for a composter. This feature was needed to prevent animals such as dogs, bears, and birds from getting into the compost. We do not want to attract these animals to the compost to avoid any safety and health issues. As well, having the compost in a closed and contained drum prevents unwanted mess and scatter of composting materials – whether from high winds or animals rummaging. Bears have strolled in the area where the composter is in place. We acquired the composter in 2015; over the years, we have not yet had issues with animals being attracted to or damaging the composter. 

Insulated drum

The average annual ambient air temperature in Fort Albany First Nation is -2 °C (28 °F).  We preferred to have a composter that included insulation to reduced potential compost temperature losses. Maintaining warm compost temperatures has allowed us to generate compost from May to October.  (The harsh winter weather where air temperatures including windchill reach -47 °C / -52.6 °F prevents us from composting year-round). Furthermore, the insulated drum design is ideal for composter geese remnants quickly and safely.  The Actium Batch Compost Drum is designed for poultry farmers to hot compost deadstock. The high temperatures reached while hot composting (> 55 °C / 131 °F) destroys potential pathogens that can be a human health risk. In Fort Albany First Nation, geese are harvested from the land and are considered a local and traditional staple food.  The remnants from processing geese (wings, feet, feathers, innards, and heads) are added into our compost drum.

Mechanically operated

Lastly, we wanted a composter that did not require electricity, but still be able to degrade organic materials effectively. The composter is placed in an area that is not close to any electrical outlets.  Additionally, we wanted a composter that did not cost money to run and was easily maintained.  The Actium Batch Compost Drum turns with the use of a crank, and the maintenance is minimal. Our maintenance tasks for the crank includes oiling moving parts and checking that the chain is in good condition. The crank also reduces labour intensity and mess (e.g. no need to shovel to turn the compost).

During the five years we have operated the Actium Batch Compost Drum in Fort Albany First Nation, we have been pleased with how the equipment operates and with the local fertilizer it creates.  The compost added to the garden soil replenishes nutrients, allowing us to continue to grow fresh, nutritious, and affordable foods in this remote far-north community. 

Composting in the Subarctic – Inputs

Boston Terrier Paisley Puppy

Greens and Browns: Composting Input Management

Actium Composting equipment allows for environmentally sustainable disposal and reuse of organic materials in the form of compost. The program I work with invested in an Actium Batch Composter Drum, to primarily create local fertilizer for subarctic community gardens located in Fort Albany First Nation, Ontario, Canada. As a secondary benefit, the Actium composter reduced the amount of organic waste accumulating in the Fort Albany First Nation’s landfill.  Community gardens are one of many types of operations that use Actium Composting Equipment. Internationally there are operations in hospitality, recreation, agriculture, landscaping, and education that use Actium Composting equipment. 

Each of these mentioned operations has a desired organic waste to be reduced.  For the Fort Albany First Nation gardening program, geese remnants and fruit and vegetable scraps were the main organic wastes to be reduced– both of these materials are known as “greens”.  These “green” materials need to be mixed with “brown” organic materials to have the hot composting process run efficiently.  This article aims to explain why “browns” need to be added with “greens” when composting, as well, to provide some general tips on composting input management.

The greens and the browns

Labelling organic materials as “greens” or “browns” helps differentiate types of materials that have a high carbon to nitrogen ratio (C:N) with materials containing a low C:N. Organic materials contain an assortment of elements, but carbon and nitrogen are the most important elements for controlling microbial activity. Carbon provides the microbes with energy, while microbes use nitrogen for protein production.  All organic materials contain more carbon than nitrogen, though the ratio between these two elements will differ depending on the organic type. Organic materials with a low C:N ratio are considered “greens” – the C:N for “greens” are 30:1 or less. Some examples of “greens” include vegetable scraps (C:N =  11:1), grass clippings (C:N = 15:1), deadstock (C:N = 5:1), and coffee grounds (C:N = 14:1).  Materials that are considered “browns” have a high C:N – greater than 30:1 – such as, straw (C:N = 53:1), wood shavings (C:N = 226:1), paper (C:N = 129:1), and dried leaves (C:N = 47:1).  A quick web browser search for “composing greens and browns” will result in resources that share lists of organic materials – and their C:N – divided into “greens” and “browns” categories.

Mixing the browns with the greens

Every addition of organic materials into a composter drum will influence the decomposing activity, and effect the C:N ratio of the compost. Knowing the C:N for each organic type added to the Actium batch composter is recommended. As well, it is suggested to aim for a compost C:N to range between 20:1 to 40:1, however the ideal compost C:N ratio is between 25:1 to 30:1. Maintaining a compost C:N of 25:1 to 30:1 helps sustain high temperatures for hot composting, also it is the most balanced diet for the best performance of decomposers. If too many “greens” are added into the compost drum, then the overall compost C:N becomes too low, releasing offensive odours, and slowing decomposition.  If too many “browns” are added, decomposition will also slow down. There are some compost mix calculators available online to help determine how much green-type and brown-type materials are needed to achieve the ideal compost C:N. Below is a table briefly indicating how much (by weight) of a brown-type material is needed for 5 lbs (2.27 kg) of a green-type material.  For example, the addition of 5 lbs of vegetable scraps into a composter drum, requires around 2.75 lbs of shredded office paper for the compost mix to have a calculated C:N of 25-30:1.

Composting Input Materials

Table:  Different types of brown-type organic materials and the weight needed of each brown-type to achieve a compost C:N ratio of 25-30:1 when mixed with 5lbs of a green-type of organic waste.   

Input-management tips for Actium Batch Composting Drums

  • Create a log to monitor the quantity and type of organics added per week  (also monitor compost temperature and moisture levels).
  • Do not add more than 50 lb (23 kg) per day of organic materials to the Actium Batch  Composting Drum.
  • Turn the compost drum every time organics are added, or at least once a week during times when there are no organic additions.
  • If the compost starts to smell, add more browns – smells indicate that the nitrogen content of the compost is too high.
  • Shred or chop organic materials to increase surface area and to improve the rate of decomposition .
  • Prevent any non-organic matter from entering the compost drum such as twist-ties, plastics, glass, metal, or other non-compostable waste as this will reduce the quality and grade of the compost.

Double-checking compost quality and performance

Those who are interested in knowing the exact C:N ratio of a finished compost batch, samples can be sent to a compost analysis service. These services – found online or locally – often can provide other compost information such as pH, nutrient content, microorganism populations, and contaminant concentrations.  The price of compost analysis differs from each company and by the number of samples and tests requested.  If compost is to be tested, it is recommended to use a well-mixed sample and to analyze more than one sub-sample to get a better representation of what is occurring in the finished compost.  Knowing the actual C:N ratio (as well as other compost analysis results) can be helpful to adjust compost management for best performance. 

Composting in the Subarctic – Moisture

Regulating Compost Moisture during Hot Composting

Hot composting is most effective at decomposing organic waste when moisture levels are approximately 50%.  A compost with excessive moisture will cause

  • Low temperatures that are below 40°C (104°F);
  • smells foul; and/or
  • brown liquid to be visible or easily freed when squeezing compost.

Excessive moisture while composting does not provide a viable environment for aerobic decomposers to thrive. Too much moisture reduces the oxygen supply to aerobic decomposers; as a result, these decomposers become less active, and compost temperatures remain low and stagnant.  Alternatively, excess moisture creates an inviting environment for the undesired anaerobic decomposers. Anaerobic decomposers are very slow at breaking down organic materials, and they create volatile acids that have a putrid smell. 

This article provides some tips on how to avoid excess moisture while using an Actium Batch Compost Drum for hot composting.

Prepping the composter

When starting a new compost batch in the Actium Compost Drum, first fill the vessel 1/4 full with dry shredded paper or dry sawdust/wood shavings.  Adding these dry and high carbon materials before other organic wastes provide a good start-up environment for aerobic decomposers, and helps the temperature to rise quickly for effective hot composting.

Consider the moisture content of organic inputs

Organic materials such as garden waste, food waste, and deadstock can all be composted; however each of these materials contains water.  For instance, vegetable peelings contain 70% of water, chicken deadstock contains approximated 67% water, and salad or juice pulp contain 90% water.  During the decomposition process, the cells of the “wet” organic materials break and release water into the greater compost pool.  With time and warm temperatures, much of the water will leave the compost through evaporation, and the wet organic materials will continue to decompose – reducing in weight and volume.  These reductions allow us to add organic waste continually over two to four months. The recommended loading rate for the Compost Drum is 50 lb (23 kg) per day.  The Compost Drum has a holding weight capacity of 2000 lb / 907 kg.  The weight capacity of the drum is not the same as the total weight of waste that can be added to the Drum.  The overall weight of waste added during a batch is much more than 2000 lb (close to double the capacity) due to the decomposing process. 

Have dry carbon and bulking agents available

It is a good habit to add dry carbon and/or bulking agents when adding “wet” organic materials to the Compost Drum. The dry carbon absorbs excess moisture, and the bulking agents improve oxygen supply. Dry carbon materials include shredded paper, shredded corrugated cardboard, wood shavings, and coconut husks.  When mixing a bulking agent with the compost, it alleviates compost compaction and allows for aeration. Examples of bulking agents include wood chips, grass clippings, autumn leaves, and chopped corn stalks.  Some bulking agents that contain little moisture can be used to aerate and absorb excess moisture, such as, peanut shells, sawdust, and straw.  As an example, if 10 lbs of food waste were added to the Compost Drum, it would be favourable to include 5 lbs of shredded paper and 2 lbs of wood chips. 

Remove excess  moisture from the composter

The Actium Batch Composter Drum is constructed to maintain high temperatures for hot composting.  The vessel of the Composter Drum has three vents (two along the sides and one on the input door) to allow for gases and water vapour to be released.  If the moisture content is too high due to insufficient additions of dry carbon materials, there will not be enough energy/heat for water to be evaporated and released through the vents as water vapour.   If the compost in the vessel becomes saturated with moisture (such as visible liquid in the vessel or liquid is easily freed when squeezing compost), then there are a couple operations that can be conduction to remove excess liquid from the vessel.

Operation 1

On a warm, dry, and sunny day,  open the input door of the drum. Turn the drum counter clock-wise until the input door is facing upwards or towards the sky.  This action allows for excess moisture to easily evaporate and escape from the vessel. Near the end of daylight hours, return to the composter and turn the vessel clock-wise to its standard position and close the input door.  Continue this operation until the moisture levels are at a point where adding dry carbon materials can correct the moisture content. 

Operation 2

Slide the input door very slightly (i.e. 1-2”) to make the door ajar.  Turn the vessel slowly clockwise. Stop turning the vessel when liquid is exiting from the input door.  Be cautious in preventing compost from pushing the ajar input door to the point that it will open.  Leave the vessel to drain for 6 to 48 hours – depending on the amount of excess moisture.  If interested in saving the liquid (a.k.a. compost tea or liquid fertilizer), collect the liquid using a large container that fits under the drum. When drainage is complete, turn the Composting Drum vessel counter clock-wise to the standard position, add dry carbon and bulking agent materials, then fully close the compost drum and turn the compost. 

The take-home message on compost moisture

Excess moisture hinders decomposition and can reduce the quality of the finished compost. Additionally, excess moisture causes unnecessary weight to the Compost Drum.  In extreme cases, when there is too much liquid in the Compost Drum, the weight can surpass capacity; this can lead to problems with the crank and chain.  Maintaining ideal moisture in the compost (approximately 50%) dedicates the volume and weight capacity of the Compost Drum to transforming up to 4500 lb of organic materials into nutrient-rich compost.

Composting Temperatures

Thermometer in Actium Batch Composter

Hot composting:

In-vessel composters, such as the Compost Drum that is manufactured by Actium Composting Equipment, creates compost quickly by using the hot-composting (also known as active-composting) technique. The key to successful hot-composting is to create a composting environment that has ample oxygen, and achieve temperatures that reach 40°C – 65°C (104°F – 149°F). This environment promotes the activity of aerobic (oxygen-loving) microorganism that rapidly break-down organic matter with temperatures that most pathogens cannot survive. Alternatively, cold-composting (also known as passive-composting) technique utilizes different microorganisms that decompose organic materials at a significantly slower rate than hot composting. Cold-composting occurs when organic materials are added to a pile and left without frequent turning – mature compost using this technique can be ready between one to two years. Cold composting typically follows the day to day air temperatures – potentially reaching higher temperatures in the center of the pile. Both aerobic and anaerobic microorganisms exist within a cold compost pile. Anaerobic microorganisms are not as efficient at breaking down organic materials compared to aerobic microorganisms. Anaerobic microorganisms flourish where there is limited to no oxygen available. Low oxygen supply occurs when compost is not turned regularly and/or there is a high supply of moisture. This article details the benefits of using the hot-composting technique, along with how temperature influences decomposition.

Benefits and drawbacks of hot-composting:

The main benefits of hot-composting include:

  • producing mature compost quickly;
  • generating a greater amount of compost in less time than a cold-compost system;
  • reaching high temperatures (> 55°C, > 131°F) within the compost that can effectively kill most weed seeds and larvae;
  • reaching high temperatures (> 55°C, > 131°F) that kill most pathogens when composting; and
  • decomposing organic materials that are difficult to decay (i.e. bones and corn cobs) at a quicker rate than when cold-composted.

The main drawback of hot-composting compared to cold-composting is that monitoring and some maintenance is needed to warrant a favourable environment for rapid aerobic decomposition throughout the composting process; which includes:

  • diversifying and mixing different organic materials to ensure a carbon to nitrogen (C:N) ratio remains within the range of 20:1 to 30:1;
  • maintaining moisture levels in the range of 40-70%;
  • ensuring adequate oxygen levels (for example, turning the organic materials regularly (after materials are added or at least once a week)
  • monitoring compost temperature to make sure it stays within the range of 40°C – 65°C (104°F – 149°F), and to observe stages of decomposer activity; and
  • monitoring compost temperature to make sure it reaches > 55°C (131°F) for at least three days for the sterilization of weed seeds, larvae, and human pathogens.

Temperature ranges for composting:

Different types of microorganisms thrive at different compost temperature ranges. The three types discussed in this article are the psychrophiles, mesophiles, and thermophiles.

Psychrophiles:

Psychrophilic microorganisms live within the cool temperature range of -10°C to 21°C (14°F to 70°F), and they actively decompose organic materials at temperatures ranging from 13°C to 21°C (55°F to 70°F). Psychrophiles are utilized when cold composting, as they decompose material at ambient temperatures. In a hot-composting environment, psychrophiles will exist only briefly – during the beginning of Spring when air temperatures become warmer, or when the very first materials are added to start composting. When the psychrophiles decompose organic materials, the
microorganisms will release heat, raising the temperature of the compost. When the compost temperature surpasses 21°C (70°F), it is no longer a viable environment for the psychrophiles, and the mesophiles begin to populate the compost. When temperatures get too warm for the psychrophiles, they either become dormant, die-off, or move to a section of the pile that is cooler.

Mesophiles:

Mesophiles will inhabit both cold-compost and hot-compost types. They live within environments that have moderately warm temperatures, ranging from 20°C to 45°C (68°F to 113°F). They are most active at decomposing materials when temperatures are between 21°C to 32°C (70°F to 90°F). Though mesophilic decomposers thrive in this temperature range, so do human pathogens (such as Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, and Salmonella sp). For these pathogens to die-off, temperatures need to increase to a point where they cannot survive.

Thermophiles:

The decomposing activity of mesophiles heat-up the compost to the point that surpasses their habitable range, and then thermophiles take over. Thermophiles can live in temperatures that destroy most pathogens. The temperature range for thermophiles is 40°C to 71°C (104°F to 160°F), and the temperature for pathogen sterilization is > 55°C (> 131°F). At high temperatures, both sterilization and decomposition are occurring. Thermophiles are very efficient decomposers − they accelerate the breakdown of complex carbohydrates, fats and proteins, and convert organics into humus – a complex material that is nutrient-rich. In a cold-compost, thermophiles are less likely to be present, but if they are, it will be most likely at the center of the pile. For hot-composting, fostering thermophiles is key to killing pathogens and decomposing organic matter rapidly. Having the ability to turn a batch or in-vessel composter is beneficial for hot composting because:

  • turning aerates the compost, providing oxygen supply to the aerobic thermophiles;
  • mixing organic matter allows thermophiles to have greater access to materials in need of sterilization or further decomposition, and;
  • turning permits equal temperature distribution, ensuring all compost materials have been sterilized and underwent thermophilic decomposition.

Achieving high temperatures is crucial for some compost operations for them to meet specific quality standards. For instance, to ensure pathogen removal, the Ontario Compost Quality Standards require temperatures to be monitored daily until > 55°C (131°F) occur for at least three consecutive days when composting most organic materials. In-vessel composters by Actium Composting Equipment are designed to help sustain temperatures where thermophiles can
thrive, and sterilization can occur; they are made with an insulated outer-layer to minimize heat escape and an optional electrical heater for maintaining a warm compost environment when operated in colder climates. As well, long-stem thermometers (Reotemp Instruments, USA) come with Actium Composters to measure compost temperatures, and to monitor when sterilizing has occurred.

Compost curing:

After the thermophiles have completed their cycle, the compost gradually cools down, and the mesophilic and psychrophilic microorganisms return. The decomposing process slows as less material is available for microorganisms to
consume. The compost is not yet complete or ready to be added to the garden. At this later stage, the compost is stabilizing as it cures. Temperatures will continue to decrease until it is near ambient temperatures, and decomposing microbial activity will eventually stop. The curing process can last a minimum of 21 days. When composting using a drum or vessel, the compost can be removed during the curing stage and placed in a secondary compost area or bin, protected from the rain.

Essentials for a Healthy Compost

Food Scraps to Compost

Macro- and micro-organisms are the workers that alter and decompose those rotting vegetables and raked leaves, into the earth smelling, dark brown crumbly substance that we call compost.  The quality of the finished compost depends on the environment we create for the organisms that do the decomposing business (a.k.a decomposers).  Just like ideal environments for many living species,  compost should provide an environment with sufficient food, temperature, water, and air.  This article briefly introduces each of these environment essentials needed for a healthy compost. 

Food:

The organic materials we add to compost can have a wide range of nutrients and minerals.  These nutritious components are why compost is considered a natural fertilizer for gardens and fields.  A healthy diet for decomposers consists of a mix of materials that contain carbon and nitrogen.  Materials such as dry fall leaves, straw, wood shavings, pine needles, twigs, newsprint, and shredded paper are high carbon sources.  Materials that have a lot of carbon are also considered “browns” in composting terminology.  These high carbon or “browns” are carbohydrate-rich and provide the energy for the decomposers.  Food scraps, livestock mortalities ( in the case of farm animal operations), grass clippings, egg shells, and coffee grounds are materials that are considered “greens” in composting terminology. These green materials contain high amounts of nitrogen, which provides protein for decomposers and helps these organisms multiply.  Both types of materials – greens and browns – should be layered and mixed to build the decomposer community and allow them to continually turn your organic waste into compost.  For instance, 1 lb of vegetable waste should be combined with at least 1 lb of newsprint.

Temperature:

With a good mix of materials and sufficient water and air, compost temperature should increase quickly.  The process of organisms decomposing materials causes the temperature of compost to rise quickly (within a few days).  Compost temperature while decomposing can range from 13°C to 71°C.  Throughout the composting process, different microbial communities take over decomposing materials, and each community prefers a different temperature range.  The ideal temperature range for efficient composting is between 32-55°C.  Below 32°C, the process of decomposition occurs but is slow.  Having compost reaches 55°C or above, the majority of microorganisms cannot survive. However, compost reaching 55°C or above for at least three days aids in sterilizing weed seeds and destroy pathogens.  

Water:

Decomposers prefer compost to have between 40% – 60% moisture.  If the compost is too dry, decomposition will slow down.  If the compost is too dry, water may need to be added or materials with a lot of moisture. More often, composts can end up being too wet. Composts with greater than 60% moisture create an anaerobic environment (low oxygen) that is inviting for undesirable micro-organisms that release bad smells in the compost.  Adding very dry “browns” to the compost mixture helps prevent the compost from becoming too wet.

Air

Aerobic decomposers (oxygen-loving organisms) are preferred for composting.  Keeping within the ideal moisture range, and turning the compost will ensure there is enough oxygen for the decomposers. Turning a batch composter every time materials are added, or once a week will help keep the compost aerated.  Furthermore, turning helps break up materials, and improves decomposers access to recently added materials. 

Managing these four factors – food, temperature, moisture, and air – are key to creating quality compost in a timely manner. Composting is not a complicated process, but these four factors should be considered if your compost starts to smell bad or if the decomposition process is slow or stagnant.